Many users set up their computers to boot Slackware Linux and another operating
system. We've described several typical dual boot scenarios below, in case you are having
difficulty setting up your system.

Setting up a computer with both MS Windows and Linux is probably the most common dual
boot scenario. There are numerous ways you can setup the booting, but this section will
cover two.

Often times when setting up a dual boot system, a person will devise a perfect plan
for where everything should go but mess up the installation order. It is very important
to understand that operating systems need to be installed in a certain order for a dual
boot setup to work. Linux always offers control over what, if anything, gets written to
the Master Boot Record. Therefore, it's always advisable to install Linux last. Windows
should be installed first, since it will always write its booter to the Master Boot
Record, overwriting any entry Linux may have put there.

Most people will want to use LILO to chose between Linux and Windows. As stated above,
you should install Windows first, then Linux.

Let's say you have a 40GB IDE hard disk as the only drive in your system. Let's also
say that you want to give half of that space to Windows and half of that space to Linux.
This will present a problem when trying to boot Linux.

20GB Windows boot (C:)
1GB Linux root (/)
19GB Linux /usr (/usr)

You would also want to set aside an adequate amount of space for a Linux swap
partition. The unwritten rule is to use twice the amount of RAM you have in disk space. A
64MB system would have 128MB of swap, and so on. Adequate swap space is the discussion of
many flames on IRC and Usenet. There's no truly “right” way to do it, but
sticking with the rule above should be sufficient.

With your partitions laid out, you should proceed to install Windows. After that is
set up and working, you should install Linux. The LILO installation needs special
attention. You will want to select the expert mode for installing LILO.

Begin a new LILO configuration. You will want to install it to Master Boot Record so
that it can be used to choose between the two operating systems. From the menu, add your
Linux partition and add your Windows (or DOS) partition. Once that's complete, you can
install LILO.

Reboot the computer. LILO should load and will display a menu letting you select
between the operating systems you have installed. Select the name of the OS you wish to
load (these names were selected when you setup LILO).

LILO is quite a configurable boot loader. It's not just limited to booting Linux or
DOS. It can boot just about anything. The man pages for lilo(8)
and lilo.conf(5) provide more detailed information.

What if LILO doesn't work? There are instances where LILO just won't work on a
particular machine. Fortunately, there is another way to dual boot Linux and Windows.

This method can be used if LILO doesn't work on your system, or if you just don't want
to set up LILO. This method is also ideal for the user that reinstalls Windows often.
Each time you reinstall Windows, it will overwrite the Master Boot Record, thus
destroying any LILO installation. With LOADLIN, you are not subject to that problem. The
biggest disadvantage is that you can only use LOADLIN to boot Linux.

With LOADLIN, you can install the operating systems in any order desired. Be careful
about installing things to the Master Boot Record, you do not want to do that. LOADLIN
relies on the Windows partition being bootable. So during the Slackware installation,
make sure you skip the LILO setup.

After installing the operating systems, copy the loadlinX.zip (where X is a version
number, such as 16a) file from root's home directory to your
Windows partition. Also copy your kernel image to the Windows partition. You will need to
be in Linux for this to work. This example shows how to do this:

That will create a C:\LINUX directory on your Windows
partition (assuming it's /dev/hda1) and copy over the necessary
stuff for LOADLIN. After doing this, you will need to reboot into Windows to setup a boot
menu.

Once in Windows, get to a DOS prompt. First, we need to make sure the system is set to
not boot into the graphical interface.

C:\> cd \
C:\> attrib -r -a -s -h MSDOS.SYS
C:\> edit MSDOS.SYS

Add this line to the file:

BootGUI=0

Now save the file and exit the editor. Now edit C:\AUTOEXEC.BAT so we can add a boot menu. The following provides
an example of what a boot menu block in AUTOEXEC.BAT would look
like:

This is the least common dual booting situation. In the days of old, LILO was unable
to boot Windows NT, requiring Linux users to hack NTLDR, which presented several more
problems than dual booting between Windows 9x and Linux. Understand that the following
instructions are deprecated. LILO has been able to boot Windows NT/2000/XP/2003 for many
years now. If you are using a legacy machine though, you may need to use just such a
hack.

Install Windows NT

Install Linux, making sure LILO is installed to the superblock of the Linux
partition

Get the first 512 bytes of the Linux root partition and store it on the Windows NT
partition

Edit C:\BOOT.INI under Windows NT to add a Linux option

Installing Windows NT should be fairly straightforward, as should installing Linux.
From there, it gets a little more tricky. Grabbing the first 512 bytes of the Linux
partition is easier than it sounds. You will need to be in Linux to accomplish this.
Assuming your Linux partition is /dev/hda2, issue this
command:

#dd if=/dev/hda2 of=/tmp/bootsect.lnx bs=1 count=512

That's it. Now you need to copy bootsect.lnx to the Windows NT partition. Here's where
we run into another problem. Linux does not have stable write support for the NTFS
filesystem. If you installed Windows NT and formatted your drive as NTFS, you will need
to copy this file to a FAT floppy and then read from it under Windows NT. If you
formatted the Windows NT drive as FAT, you can simply mount it under Linux and copy the
file over. Either way, you will want to get /tmp/bootsect.lnx
from the Linux drive to C:\BOOTSECT.LNX on the Windows NT
drive.

The last step is adding a menu option to the Windows NT boot menu. Under Windows NT
open a command prompt.

C:\WINNT> cd \
C:\> attrib -r -a -s -h boot.ini
C:\> edit boot.ini

Add this line to the end of the file:

C:\bootsect.lnx="Slackware Linux"

Save the changes and exit the editor. When you reboot Windows NT, you will have a
Linux option on the menu. Choosing it will boot into Linux.